Wikipedia:Categories

This page is a guideline on the Simple English Wikipedia.Many editors agree with the ideas on this page. It is a good idea to follow it, but it is not policy. You can change the page as needed, but please use the talk page to make sure that other editors agree with any big changes.

Categories are pages that are used to group other pages on similar subjects together. This is done to help users find the pages they are looking for, even if they do not know whether it exists or what it is called.

Every page should belong to at least one category. A page may often be in several categories. However, putting a page in too many categories may not be useful.

If you are confused or uncertain about the categories on a page, add {{Uncat}}. The main use of this template is to show that the page needs to have categories added to it. This may mean that it has no categories. It can also be used if the page may be missing categories or be in the wrong category. Users with experience dealing with categories will look at the page and help fix the categories.

Categories are all a part of what is called the Category Tree. Each category is a sub-category, or child, of a more general category, the parent category. The category tree is made up of two main parts. These two parts are Articles and Wikipedia. As the name says, the section on articles deals with all of the articles. The section on Wikipedia is for all pages which are not articles. These include pages in the Wikipedia: namespace and templates.

The article categories are separated into nine major groups: Everyday life, Geography, History, Knowledge, Language, Literature, People, Religion, and Science. Each of these groups is separated into smaller groups or sub-categories which have even smaller groups inside them. The main categories are said to be at the top of the Category Tree and each sub-category is one step below them. The farther down the category tree a category is, the more precisely it groups the pages in it.

Pages are put into categories by placing one or more Category tags on the page. Category tags are the wiki markup used by the Wikimediasoftware to put pages in categories. The format for a Category tag is:

It is usually best to put a page in the categories which are most specific to it, rather than in all the categories which might be related. Pages should be placed in the lowest level of the category tree that applies to them. Pages should never be placed in both the parent and child categories. They should not be placed in a category and any of the categories above it. This means if a page is placed in a category, it should not be placed in any of the parent categories of that category, or any parent categories of that category's parents, and so on, moving up the category tree. It may be placed in categories in different sections of the category tree, but not in those directly above it.

Because Category:Brass instruments is a sub-category of Category:Musical instruments, Trombone should not be put into both categories. If all the hundreds of types of musical instruments are put into the parent Category:Musical instruments, that category will get too full to be useful in helping users to find the pages they are looking for, which is the true purpose of the category system. It is easier for the user to browse Category:Musical instruments and see several sub-categories such as Category:Brass instruments, Category:Woodwind instruments, etc. This lets the user select the one they want and browse the smaller number of pages listed there. It takes one more click, but less time than searching a very large category.

Many times the most correct category may not exist yet. When this happens, a new category may be created (see: Creating new categories before doing this) or the article is placed in the lowest existing category that applies to it. This may require using more than one category.

Categories should be placed near the end of an article. They should be after the body of the article and any templates it uses but before the links to the page on Wikipedias in other languages. Categories should be listed in order of importance. The reasons for notability should be listed first and minor categories such as birth and death (or the {{BD}} template) should be listed last.

Because categories are a way to group together similar articles, there is no need to create a new category for just one or two articles. There should be a minimum of three articles that would fit into the category before a new category is created. Sub-categories should be considered when a category starts to get too large to easily find an article in it. There is no set number of articles to require this, but if a category has more than twenty articles, it is usually a good time to think about dividing it into smaller sub-categories.

The names of categories should be kept as short as possible but still explain what the category is for. Category names should not be ambiguous. If a possible name for the category has more than one meaning, it is probably better to find a different name or change it in a way that only has one meaning. For example, Georgia has two meanings. It is the name of a country in eastern Europe and a state in the United States. If the category was named Category:Georgia, it could mean either of them. This could cause people to put the wrong articles in the category. Category:Georgia (country) only has one meaning: the country in Europe. It is a better name for the category.

Naming conventions should also be followed when naming new categories. Similar categories should have similar names. This makes it easier to know which category to use and helps stop people from creating a new category that is the same as one that already exists. It is best to look at what categories you will be putting the new category into and see how other categories there are named. This should give you a basic idea of what form the name should be in.

There are several basic forms of names used in categories:

Form

Example

Uses

in country

Cities in Italy

In is used when dealing with things located in a location such as a country. Physical objects which do not leave the area use this format. Examples: Cites and Mountains. Because of the number of categories for Rivers already created, Rivers use the "of" country form.

of country

Politics of Germany

Of is used thing from a country or belonging to a country. These may or may not be physical thing. In some cases, of is used for people. This is most often when the adjective to describe the people is difficult to use or can mean different things. An example is Category:People of the Philippines.

by country

Rivers by country

This form is used to group several subcategories together. It is used to group categories dealing with different countries that do not deal with people.

by nationality

Singers by nationality

This form is used in the same way as by country, but it is used for categories dealing with people.

As with all pages, Categories should have a short statement that says what they are about. If there is an article that defines the category, the template {{catmore|Article name}} can be used to show the main article for the category. If no article exists, you should write one or two sentences to explain the category. Interwiki links to the same categories on Wikipedias in other languages should also be added to the page.

When placing pages in categories, it is important that they be sorted correctly. This makes it easier to locate a page in the category. Sorting of pages in a category is done by use of a sort key. A sort key is a term or phrase that is used to sort pages in categories. Pages are sorted alpha-numerically by their sort key. If no sort key is used, the page name of the page is used as the default sort key. {{DEFAULTSORT:}} can be used to change the default sort key for the entire page. Sort keys may be given to each category tag individually. A sort key is added to a category by using a pipe character ( "|" ) followed by how the article should be sorted. All characters after the pipe character are used as part of the sort. This includes spaces and special characters. Categories are sorted first by special characters, then letters.

Examples

(Using an article named "River Thames")

wiki-code

effect

[[Category:Rivers in England]]

This category has no sort key so it would be sorted by its page title under the letter R - River Thames

[[Category:Rivers in England |Thames, River]]

This article would be sorted under the letter T - Thames, River

{{DEFAULTSORT:Thames, River}}[[Category:Rivers in England]]

The default sort key for the article is changed from its title, River Thames, to Thames, River. This causes the article to be sorted under T.

[[Category:Rivers in England |Thames, River]][[Category:London]]

Sort keys can be mixed on a page. Here, the article is placed under T in Category:Rivers in England and under R in Category:London.

The default sort key for the article is changed from its title, River Thames, to Thames, River. Because Category:Rivers in England does not have a sort key, it uses the one given in the {{DEFAULTSORT}} and gets sorted under T. Category:London uses the sort key of the category tag and sorts it under R.

Generally, pages are sorted by their title. There are cases when this is usually done. Most of these are when the first word of the title is not the most important thing in the title. Pages that start with the word The, the word A, or the word An (for example The Doors, A Tale of Two Cities, An Inconvenient Truth) should not be sorted by title. Another common case are lists, for example List of German composers. The sort key should be used to put either remove these words or place them at the end.

Page title

Sort key

The Sound of Music

Sound of Music, The

A Tale of Two Cities

Tale of Two Cities, A

An Inconvenient Truth

Inconvenient Truth, An

List of German composers

German composers, List of

Different ways of sorting are also used when the article name is a very common term in the category it is used in. For example, in Category: Cities in the United States, most of the subcategories have very similar names. There are many sub-categories that use the name Cities in and the name of the state. To make it easier to locate one subcategory quickly, the subcategories are listed by the name of the state rather than their title. This is also common in categories based on nationality. For example Category:German entertainers is sorted in the Category:German people under the sort key Entertainers because most of the other subcategories will also be using the term German in their title.

Names of persons

When dealing with articles on people, the article should be sorted by the person's family name. See Sorting of people for more information.

Special character sort keys

In certain cases, articles are sorted using a sort key that is entirely different from their title. This is common when the article is either the main article for the category or defines the category in some way. For example, in Category:U.S. states, the article States of the United States is the main article. It defines what the category is about. The article List of U.S states would also define the category, but in a different way. These articles are sorted using special characters which make them be sorted at the top of the list articles in a category. Special character sort keys are used in the same way as regular sort keys. The special character is the first character used after the pipe character. Special character sort keys are sorted by the entire sort key. If more than one article in a category uses the special character, they are sorted together, but do not sort alphabetically unless the rest of the title is used in the sort key. For example, [[Category:Rivers in England| ]] is sorted with a sort key that is a Space bar character. If another page uses the same category tag, they are both sorted together, but may not be in alphabetic order. If [[Category:Rivers in England|*River Thames]] were used, the article would be sorted under the asterisk character and if any other articles were sorted under the asterisk in this same way ([[Category:Rivers in England|*Rivers in London, List of]]) they would all be sorted under the asterisk and then sorted alphabetically by the rest of the sort key.

Character

Use

Space

The space character is the first character when sorted. This character is used for the main article.

*

The asterisk is used to help define the category. These are usually lists of articles that belong in the category.

!

The exclamation point is used for articles that are very important, but not defining the category. This character is rarely used.

β

Greek letter beta; used for Wikipedia books

Σ

Greek letter sigma; used for putting stub categories into other categories

More than one sort key may be used on a page. This is common when the page title is the correct way to sort for one category, but in other categories it needs to be sorted a different way. For example Category:German entertainers would be sorted as Entertainers in Category:German people, but be sorted as German entertainers in Category:Entertainers.

When categorizing people, it is usual to have at least four categories. These categories are the year the person was born, the year they died, their nationality, and their reason for being notable. Each article on a person should have the information for these categories. This information is likely to be in the first sentence of an article:

A person can be listed in more than one category based on nationality. If the person is of a nationality on country, has a citizenship a different country, and their recent ancestry (they are a child of immigrant parents) for another country, they are usually categorized as a member of each group of people listed.

It is common for a person to fit into more than one category based on what they are known for. A person should be listed in each category he qualifies for. Each article should have at least one category of this type but there are articles when this does not apply. One example of when no notability category is used is for victims of a crime who are notable because of the large amount of media about the crime. Azaria Chamberlain is an example of this.

In most cases, nationality and notability will combine in a single category (German musicians, German politicians, German physicists). This is an exception to the minimum of four categories because it combines two of the categories needed into one category.

When creating combined categories such as these, it is important that the category itself is a sub-category of each of its main categories. For example, Category:German politicians is a sub-category of both category:German people and Category:Politicians. Because of this, a person who is put into Category:German politicians is categorized as being both a German person and a politician.

When a person is added to a category, their name needs to be sorted so that it is listed in a way that is easy to find. This is done by adding a Sort key to the category. For most people, their name is sorted as Last name, First name. In the example above, this would be Smuckateli, Joe. In this way, they are listed in the category alphabetically by their last name. This is done in one of two ways.

Default sorting

The tag {{DEFAULTSORT:}} can be used. It will give the same sort key to every category tag on the page that does not have a sort key of its own. To use the Default sort, the line {{DEFAULTSORT:Sort key}} is used. Sort key is replaced with how the articles is to be sorted. For example {{DEFAULTSORT:Smuckateli, Joe}}.

Individual sorting

Each category tag may be given its own sort key. This is done by adding a pipe character ( "|" ) and then information after the category name. For example [[Category:German musicians |Smuckateli, Joe]]
[[Category:Wikipedia]]. If a space is used after the pipe character, the category will be sorted using that space. This will place the article at the top of list in the category. This should not be done with people articles.

Other cases

If no sort key is used, the article will be sorted using its title. People whose articles only have one name (Madonna), or if the article title is how it should be sorted (Elizabeth II of the United Kingdom) do not need to have a sort key used. Articles about people with eastern Asian names need extra attention when sorting. Many eastern Asian names have the surname or family name first and the given name second. These names do not need to be sorted because when they are sorted by the article title, they are being sorted by the surname. This is not always true, some Asian people use a Western style of naming and need to have their names sorted.

The template {{BD}} (Born/Died) is useful for dealing with categories for birth and death. See its page for help with using it. It also includes a how the person is sorted in the category. This means that the DEFAULTSORT template mentioned above does not need to be used. This causes less work because this information does not need to be added to all of the categories used in the article.